Data transmission apparatus control method, data transmission apparatus control unit, data transmission apparatus, data transmission apparatus control program, and recording medium containing the program

ABSTRACT

A data transmission apparatus includes a plurality of I/F (interface) units for converting data into a predetermined transmission format and transmitting it to an external device, a power source section for supplying electric power to the I/F sections, a control section for controlling the power source section, and detection sections are connected to the external device and outputting connection detecting signals to the control section. The control section outputs a power control signal to the power source section so as to operate in such a manner that when the control section has detected that at least one of the I/F sections is in a connecting state, the electric power is supplied to the I/F sections, and when the control section has detected that none of the I/F sections is in a connecting state, no electric power is supplied from the power source section to the I/F sections.

TECHNICAL FIELD

[0001] The present invention relates to a data transmission apparatusthat transmits data outward and that is utilized for a system thatcarries out data processing or signal communication. The presentinvention relates more particularly to power saving of an interfacesection (hereinafter referred to as an I/F section) of the datatransmission apparatus, the I/F section transmitting the data.

BACKGROUND ART

[0002] Data processing apparatus such as a computer ortelecommunications apparatus such as a modem or an exchanger includes adata transmission apparatus for exchanging information with the outsideworld. The data transmission apparatus includes a plurality of I/Fsections each for transmitting data outward.

[0003] In general, the I/F section has a tendency to large powerconsumption as compared with other circuits in the apparatus. This isbecause the I/F section transmits the data outward. Especially, thetendency is remarkable in the case of outputting electromagnetic wavesor laser light outward or in the case where many I/F sections areprovided.

[0004] For this reason, in portable devices that is especially requiredto save the power consumption, a data transmission apparatus includes aplurality of power source units for supplying the respective I/Fsections with electric power. It is widely adopted that the power sourceunits control the supplying of the electric power to the I/F sectionssuch that the power source units stop supplying of the electric power tothe I/F sections that have no outside inputting/outputting of signals.When the power source units delicately control the supplying of theelectric power to the I/F sections, the data transmission apparatus cansave the power consumption.

[0005] However, the data transmission apparatus causes the increase ofthe number of components, the increase of the manufactures' cost, andthe increase of the size of the apparatus. This is because the datatransmission apparatus needs plural power source units whose number isequal to the number of the I/F sections.

[0006] Further, the following inexpediency arises, depending on whatkind of signals are inputted and outputted between the I/F sections anda control unit for outputting data to the I/F sections. Morespecifically, when a data is supplied to the I/F section while the powersource unit stops supplying of the electric power to the I/F section, aninternal circuit of the control unit or the I/F section is likely to bebroken down.

[0007] Still a further, the problem arises that the reduction of thepower consumption is not possible for an apparatus in which a powersource unit does not carry out the above power control with respect toan I/F section.

DISCLOSURE OF INVENTION

[0008] In view of the foregoing conventional problems, the presentinvention was made, and its object of the present invention is toprovide a data transmission apparatus control method, a datatransmission apparatus control unit, a data transmission apparatus, adata transmission apparatus control program, and a recording mediumcontaining the program, each capable of reducing the power consumptionof I/F sections in the data transmission apparatus.

[0009] In order to achieve the object, a control method of a datatransmission apparatus, in accordance with the present invention, whichincludes: (a) a plurality of I/F sections, each converting a data into apredetermined transmitting format and transmitting it to an externaldevice; (b) a power source section that supplies electric power to therespective I/F sections; and (c) detection sections each detectingwhether or not each of the I/F sections is in a connecting state withrespect to the external device, is characterized by including the stepof: controlling the electric power such that the electric power issupplied to all of the I/F sections from the power source section whenthe detection sections detect that at least one I/F section is in aconnecting state, and such that no electric power is supplied to the I/Fsections from the power source section when the detection sectionsdetect that none of the I/F sections is in a connecting state.

[0010] In the control method, the term “a connecting state” indicates astate in which the I/F section can transmit the data to the externaldevice. For example, the I/F section and the external device may beconnected via a wire such as an optical cable, so as to realize such aconnecting state. Alternatively, the I/F section and the external devicemay be connected by wireless such as electromagnetic waves, so as torealize such a connecting state. The connecting state may be a state inwhich the I/F section can transmit the data to the external device, butis not required to be a state in which the external device can receivethe data. On this account, for example, a state, in which a cable fortransmitting the data to the external device is connected to the I/Fsection, can be regarded as that the I/F is in a connecting state.

[0011] According to the control method, it is controlled such that theelectric power is supplied to all of the I/F sections from the powersource section when at least one I/F section is in the connecting state.This allows the electric power to be supplied to the I/F section whichis in a connecting state, so as to transmit the data to the externaldevice. In contrast, it is controlled such that the electric power issupplied to none of the I/F sections from the power source section whenthe detection sections detect that none of the I/F sections is in aconnecting state. This ensures that the power consumption of all of theI/F sections becomes zero.

[0012] Thus, in the control method of the present invention, it ispossible to save the power consumption when none of the I/F sections isin a connecting state. Further, the provision of a single power sourcesection ensures that the number of the components is reduced comparedwith the case where the power source sections whose number is equal tothat of the I/F sections are provided for the purpose of saving thepower consumption.

[0013] Another control method of a data transmission apparatus, inaccordance with the present invention, which includes: (a) a pluralityof I/F sections and (b) detection sections, is characterized byincluding the step of controlling so as: to output the data to an I/Fsection, when the detection sections detect that the I/F section is in aconnecting state when transmitting the data to the external device viathe I/F, and (a) to output a signal to the I/F section, the signalcausing the I/F section to transmit to the external device a signalwhose output level is a low level, or (b) not to output the data to theI/F section, when the detection sections detect that the I/F section isnot in a connecting state.

[0014] In the control method, it is controlled such that the data isoutputted to the I/F section, when the I/F section is in a connectingstate when transmitting the data to the external device via the I/F.This allows the I/F section which is in a connecting state to transmitthe data to the external device. In contrast, it is controlled such that(1) a signal is outputted to the I/F section, the signal causing the I/Fsection to output to the external device a signal whose output level isa low level, or (2) the data is not outputted to the I/F section, whenthe I/F section is not in a connecting state. This causes the outputlevel of the I/F section which is not in a connecting state to be a lowlevel or zero, thereby ensuring to realize the saving of the powerconsumption.

[0015] Thus, according to the data transmission apparatus control methodof the present invention, it is possible to save the power consumptionwith respect to the I/F section that is not in a connecting state, evenin a data transmission apparatus which does not carry out the saving ofthe power consumption based on the electric power control of the I/Fsection.

[0016] A data transmission apparatus including a control unit inaccordance with the present invention includes: a plurality of interfacesections; a power source section; a control unit that controls the powersource section; detection sections each detecting whether or not each ofthe interface sections is in a connecting state with respect to theexternal device, and outputting a connecting detection signal to thecontrol unit. The control unit is characterized by including a powercontrol section that outputs to the power source section a power controlsignal for controlling the electric power such that the electric poweris supplied to all of the I/F sections from the power source sectionwhen it is detected that at least one I/F section is in a connectingstate, and such that no electric power is supplied to the I/F sectionswhen it is detected that none of the I/F sections is in a connectingstate.

[0017] In the data transmission apparatus, each of the detectionsections outputs the connecting detection signal which varies dependingon the connecting state of each I/F section. The control unit outputs tothe power source the power control signal which varies depending on theconnecting detection signal, and the power source section supplies ordoes not supply the electric power to the I/F sections in accordancewith the power control signal.

[0018] The control unit including the above arrangement outputs to thepower source section a power control signal for controlling the electricpower such that the electric power is supplied to all of the I/Fsections from the power source section when it is detected that at leastone I/F section is in a connecting state. In contrast, the control unitoutputs to the power source section a power control signal forcontrolling the electric power such that no electric power is suppliedto the interface sections when it is detected that none of the I/Fsections is in a connecting state.

[0019] At this time, in the data transmission apparatus, the electricpower is supplied to all of the I/F sections from the power sourcesection in accordance with the controlling of the control unit, when itis detected that at least one I/F section is in a connecting state. Thisallows the electric power to be supplied to the I/F section which is ina connecting state, so as to transmit the data to the external device.In contrast, no electric power is supplied to the I/F sections inaccordance with the controlling of the control unit when it is detectedthat none of the I/F sections is in a connecting state. This allows thepower consumption of all of the I/F sections to become zero.

[0020] Although a single power source section is provided in the datatransmission apparatus, in which the control unit is included, of thepresent invention, it is possible to save the power consumption with fewcomponents. This is because it is possible to save the power consumptionwhen none of the I/F sections is in a connecting state.

[0021] A data transmission apparatus including a control unit inaccordance with the present invention, includes: a plurality ofinterface sections; a control unit that controls outputting of the datato the interface sections; and detection sections. The control unit ischaracterized by including an output control section that controls thecontrol unit in accordance with the connecting detection signal suchthat: when the detection section detects that the I/F section which isin process of outputting a data to be transmitted to the external deviceis in a connecting state, the data is outputted to the I/F section, andwhen the detection section detects that the I/F section which is in aprocess of outputting the data to be transmitted to the external deviceis not in a connecting state, (a) a signal is outputted to the I/Fsection, the signal causing the I/F section to output to the externaldevice a signal whose output level is a low level, or (b) the data isnot outputted to the I/F section.

[0022] In the data transmission apparatus, each of the detectionsections outputs to the control unit a connecting detection signal whichvaries depending on a connecting state of each I/F section. The controlunit outputs the data to the I/F section in response to the connectingdetection signal.

[0023] With the control unit including the above arrangement, the outputcontrol section outputs the data to an I/F section which is in a processof outputting the data to be transmitted to the external device, whenthe I/F section is in a connecting state. This allows the I/F section,which is in a connecting state, to transmit the data to the externaldevice. In contrast, when the I/F section which is in a process ofoutputting the data to be transmitted to the external device is not in aconnecting state, it is controlled such that (a) a signal is outputtedto the I/F section, the signal causing the I/F section to output to theexternal device a signal whose output level is a low level, or (b) thedata is not outputted to the I/F section. This causes the output levelof the I/F section to become a low level or zero, thereby realizing thesaving of the power consumption.

[0024] Thus, it is possible for a data transmission apparatus includinga control unit of the present invention to save the power consumptionwith respect to the I/F section that is not in a connecting state, evenin a data transmission apparatus which does not carry out the saving ofthe power consumption based on the electric power control of the I/Fsection.

[0025] A data transmission apparatus in accordance with the presentinvention, is characterized by including: a plurality of I/F sections;at least one power source section; one of the control units having theabove-described respective features; and detection sections.

[0026] With the data transmission apparatus having the above describedarrangement, it is possible to obtain the same effect as the foregoingeffect.

[0027] It is possible for a computer to carry out the control method ofthe data transmission apparatus, when a control program corresponding tothe control method of the data transmission apparatus is executed by thecomputer. When the control program of the data transmission apparatus isrecorded in a computer-readable recording medium, it is possible for anycomputer to carry out the control method of the data transmissionapparatus.

[0028] For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuring detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0029]FIG. 1 is a block diagram showing a schematic arrangement of adata transmission apparatus of one embodiment in accordance with thepresent invention.

[0030]FIG. 2 is a block diagram showing a schematic arrangement of acontrol section shown in FIG. 1.

[0031]FIG. 3 is a truth table for a control circuit shown in FIG. 2, thetruth table showing a logical level of a connecting detection signal anda logical level of a corresponding power control signal.

[0032]FIG. 4 is a block diagram showing a schematic arrangement of acontrol section of a data transmission apparatus of another embodimentin accordance with the present invention.

[0033]FIG. 5. is a truth table for a control circuit shown in FIG. 4,the truth table showing a logical level of a connecting detectionsignal, and a logical level of a corresponding power control signal, anda logical level of an output level control signal.

[0034]FIG. 6 is a block diagram showing a schematic arrangement of acontrol section of a data transmission apparatus of a further embodimentin accordance with the present invention.

[0035]FIG. 7. is a truth table for a control circuit shown in FIG. 6,the truth table showing a logical level of a connecting detectionsignal, and a logical level of a corresponding power control signal, alogical level of an output level control signal, and a logical level ofan output buffer control signal.

[0036]FIG. 8 is a block diagram showing a schematic arrangement of adata transmission apparatus of still a further embodiment in accordancewith the present invention.

[0037]FIG. 9 is a block diagram showing a schematic arrangement of acontrol section shown in FIG. 8.

[0038]FIG. 10. is a truth table for a control circuit shown in FIG. 9,the truth table showing logical levels of respective connectingdetection signal and mode signal, a logical level of a correspondingpower control signal, a logical level of an output level control signal,and a logical level of an output buffer control signal.

[0039]FIG. 11 is a block diagram showing a schematic arrangement of anembodiment which is applied to an IEEE Std 1394 serial bus standard.

BEST MODE FOR CARRYING OUT THE INVENTION

[0040] (First Embodiment)

[0041] The following description deals with a first embodiment withreference to FIG. 1 through FIG. 3.

[0042]FIG. 1 is a block diagram showing a schematic arrangement of adata transmission apparatus of one embodiment in accordance with thepresent invention. The data transmission apparatus 1 includes: three I/Fsections 2 a, 2 b, and 2 c for transmitting data to external devices viaoptical communications; a single power source section 3 for supplyingthe electric power to the I/F sections 2 a through 2 c; a controlsection 4 (a control unit) for controlling the I/F sections 2 a through2 c and the power source section 3, respectively; and detection sections5 a, 5 b, and 5 c for detecting whether or not the respective I/Fsections 2 a through 2 c are in a connecting state and for transmittingrespective connecting detection signals to the control section 4.

[0043] Plugs 6 a and 6 b are provided so as to be connected ordisconnected with the I/F sections 2 a through 2 c, respectively. Theplug 6 a corresponds to one terminal of an optical fiber 7 a. The plug 6b corresponds to one terminal of an optical fiber 7 b. Note that plugs(not shown) corresponding to the other terminals of the respectiveoptical fibers 7 a and 7 b are connected with an external device (notshown). Note also that it is judged in the present embodiment andsubsequent embodiments whether or not the respective I/F sections 2 athrough 2 c are in a connecting state based on whether or not therespective plugs are put in the I/F sections 2 a through 2 c. Further,note that the inputting and outputting of data signals 101 a through 101c, each being an electrical signal, are carried out between the controlsection 4 and the I/F sections 2 a through 2 c, respectively.

[0044] Each of the I/F sections 2 a through 2 c includes a lightemitting element which converts an electrical signal into an opticalsignal and a light receiving element which converts an inputted opticalsignal into an electrical signal. The data signals 101 a through 101 c,each being an electrical signal, that have been supplied to therespective I/F sections 2 a through 2 c from the control section 4 areconverted into optical signals by the respective light emittingelements. The optical signals thus converted are outputted to theexternal device via the plugs 6 a and 6 b and the optical fibers 7 a and7 b, respectively. On the other hand, the optical signals, that havebeen supplied to the I/F sections 2 a through 2 c as the data signalfrom the external device via the optical fibers 7 a and 7 b and theplugs 6 a and 6 b, are converted into electrical signals by therespective light receiving elements. The electrical signals thusconverted are outputted to the control section 4 as the data signals 101a through 101 c, respectively.

[0045] When the electric power is supplied to the I/F sections 2 athrough 2 c from the power source section 3 via a power supply line 8,the I/F sections 2 a through 2 c operate, respectively. The power sourcesection 3 supplies the electric power or stops supplying of the electricpower in accordance with a power control signal 102 supplied from thecontrol section 4.

[0046] According to the present embodiment, it is assumed that (a) thepower control signal 102 is a digital signal, (b) when the power controlsignal 102 has a logical level of “1”, the power source section 3supplies the electric power to the I/F sections 2 a through 2 c,respectively, and (c) when the power control signal 102 has a logicallevel of “0”, the power source section 3 stops supplying of the electricpower to the I/F sections 2 a through 2 c, respectively.

[0047] The detection sections 5 a through 5 c detect whether or not theplugs are put in the I/F sections 2 a through 2 c, respectively, andoutput the connecting detection signals 103 a through 103 c to thecontrol section 4, respectively. According to the present invention,when the detection sections 5 a through 5 c detect that the plugs areput in the I/F sections 2 a through 2 c (hereinafter this state will bereferred to as a connecting state), the detection sections 5 a through 5c output the respective connecting detection signals 103 a through 103 cwhose logical levels are “1”. On the other hand, when the detectionsections 5 a through 5 c detect that the plugs are not put in the I/Fsections 2 a through 2 c (hereinafter this state will be referred to asa nonconnecting state), the detection sections 5 a through 5 c outputthe respective connecting detection signals 103 a through 103 c whoselogical levels are “0”.

[0048] The control section 4 modulates (a) an electric signal that hasbeen supplied as an input/output signal 104 from an external device suchas a computer to (b) an electric signal that has a transmitting formatsuitable for optical communications. The electric signal thus modulatedis outputted to the I/F sections 2 a through 2 c as the data signals 101a through 101 c, respectively. Note that the control section 4 mayoutput the data signal to one of the I/F sections 2 a through 2 c inaccordance with the information contained in the input/output signal104. Alternatively, the control section 4 may simultaneously output thedata signals to all the I/F sections 2 a through 2 c, respectively.

[0049] The control section 4 demodulates (a) electric signals that havebeen supplied as the data signals 101 a through 101 c from the I/Fsections 2 a through 2 c, respectively, to (b) electric signals thathave an appropriate transmitting format. The electric signals thusdemodulated are outputted to the external device as the input/outputsignal 104. For example, these modulations and demodulations are theconversions such as protocol conversions, analog-digital conversions, orparallel-serial conversions. The control section 4 also (i) generatesthe power control signal 102 in response to the connecting detectionsignals 103 a through 103 c that have been supplied from the detectionsections 5 a through 5 c, respectively, and (ii) outputs the powercontrol signal 102 thus generated to the power source section 3.

[0050]FIG. 2 is a block diagram showing a schematic arrangement of thecontrol unit 4. The control unit 4 includes a modulation/demodulationcircuit 10, a control circuit 11 (power control section), buffercircuits 12 a, 12 b, 12 c, 13 a, 13 b, and 13 c, respectively. In themodulation/demodulation circuit 10, the conversions of transmittingformats are carried out between the input/output signal 104 and the datasignals 101 a through 101 c. The control section 11 (i) generates thepower control signal 102 in response to the connecting detection signals103 a through 103 c that have been supplied from the detection sections5 a through 5 c, respectively, and (ii) outputs the power control signal102 thus generated to the power source section 3. The buffer circuits 12a through 12 c and 13 a through 13 c adjust voltage levels and currentlevels between the modulation/demodulation circuit 10 and the I/Fsections 2 a through 2 c, respectively.

[0051] Further, the buffer circuits 12 a through 12 c and 13 a through13 c may temporally store the respective data signals 101 a through 101c that are transmitted or received. In this case, the buffer circuits 12a through 12 c can prevent a disappearance of data. Such a disappearanceoccurs when a transmitting speed, for the data signals 101 a through 101c that are outputted to the I/F sections 2 a through 2 c from themodulation/demodulation circuit 10, is faster than a processing speedfor the data signals 101 a through 101 c in the respective I/F sections2 a through 2 c. The buffer circuits 13 a through 13 c can prevent adisappearance of data. Such a disappearance occurs when a transmittingspeed, for the data signals 101 a through 101 c that are outputted tothe modulation/demodulation circuit 10 from the respective I/F sections2 a through 2 c, is faster than a processing speed for the data signals101 a through 101 c in the modulation/demodulation circuit 10.

[0052]FIG. 3 is a truth table for the control circuit 11, the truthtable showing a logical level of connecting detection signals 103 athrough 103 c and a logical level of a corresponding power controlsignal 102. The operation in accordance with the truth table is realizedby a logical circuit represented by a logical formula of L(102)=L(103a)+L(103 b)+L(103 c). Here, it is assumed that L(x) indicates a logicallevel of a signal x, and “+” indicates a logical sum.

[0053] As is clear from FIG. 3, the control circuit 11 outputs to thepower source section 3 a power control signal 102 having a logical levelof “0”, when all the logical levels of the connecting detection signals103 a through 103 c are “0”, i.e., only when none of the I/F sections 2a through 2 c is in a connecting state, whereas the control circuit 11outputs to the power source section 3 a power control signal 102 havinga logical level of “1”, when at least one of the connecting detectionsignals 103 a through 103 c has a logical level of “1”, i.e., only whenat least one of the I/F sections 2 a through 2 c is in a connectingstate.

[0054] In a data transmission apparatus 1 having the above arrangement,when at least one of the I/F sections 2 a through 2 c is in a connectingstate, at least one of the connecting detection signals 103 a through103 c, that are supplied to the control circuit 11 of the controlsection 4 from the detection sections 5 a through 5 c, has a logicallevel of “1,”. As is clear from FIG. 3, the control circuit 11 generatesa power control signal 102 having a logical level of “1”, and outputs itto the power source section 3. The power source section 3 supplies theelectric power to all the I/F sections 2 a through 2 c, so as to operateall the I/F sections 2 a through 2 c.

[0055] In this case, when the input/output signal 104 is supplied to themodulation/demodulation circuit 10 of the control section 4, themodulation/demodulation circuit 10 modulates the input/output signal 104to an electrical signal having an appropriate transmitting format, andoutputs the electrical signal thus modulated to the I/F sections 2 athrough 2 c as the data signals 101 a through 101 c via the buffercircuits 12 a through 12 c, respectively. The I/F sections 2 a through 2c converts the data signals 101 a through 101 c (electrical signal) intooptical signals, and transmits the optical signals to an external devicevia the plugs 6 a and 6 b and the optical fibers 7 a and 7 b,respectively.

[0056] When optical signals are supplied to the I/F sections 2 a through2 c from the external device via the optical fibers 7 a and 7 b and theplugs 6 a and 6 b, respectively, the I/F sections 2 a through 2 cconvert the optical signals into electrical signals, and outputs them asthe data signals 101 a through 101 c to the modulation/demodulationcircuit 10 of the control section 4 via the buffer circuits 12 a through12 c of the control section 4, respectively. The modulation/demodulationcircuit 10 modulates the data signals 101 a through 101 c to anelectrical signal having an appropriate transmitting format, and outputsthe electrical signal thus modulated to the external device as theinput/output signal 104.

[0057] In the data transmission apparatus 1, when none of the I/Fsections 2 a through 2 c is in a connecting state, all the connectingdetection signals 103 a through 103 c, which are supplied to the controlcircuit 11 of the control section 4 from the detection sections 5 athough 5 c, have a logical level of “0”, respectively. As is clear fromFIG. 3, the control circuit 11 generates a power control signal 102having a logical level of “0”, and outputs it to the power sourcesection 3. The power source section 3 stops supplying of the electricpower to all the I/F sections 2 a through 2 c, such that all the I/Fsections 2 a through 2 c stop operating. Thus, the power consumption inthe I/F sections 2 a through 2 c becomes zero.

[0058] In this case, the I/F sections 2 a through 2 c will never convertthe data signals 101 a through 101 c into the optical signals and suchoptical signals will never be transmitted to the external device, evenwhen the input/output signal 104 is supplied to themodulation/demodulation circuit 10 of the control section 4 and when themodulation/demodulation circuit 10 outputs the data signals 101 athrough 101 c to the I/F sections 2 a through 2 c via the buffercircuits 12 a through 12 c, respectively. This is because the I/Fsections 2 a through 2 c stop operating.

[0059] Thus, the data transmission apparatus 1 of the present embodimentcan save the power consumption of the I/F sections 2 a through 2 c onlyby including a single power source section 3. Accordingly, it ispossible for the data transmission apparatus 1 to realize the saving ofthe power consumption with fewer components than a case where each ofthe I/F sections 2 a through 2 c has a power source section.

[0060] When the light emitting elements of the I/F sections 2 a through2 c emit the light having great intensity or emit coherent light, thefollowing should be noted. More specifically, if the light emittingelements emit the light without putting the plugs 6 a and 6 b in the I/Fsections 2 a through 2 c, it is likely that the eyes of a user will beinjured. In contrast, according to the data transmission apparatus ofthe present embodiment, it is possible to eliminate the risk. This isbecause all the I/F sections 2 a through 2 c stop operating when none ofthe I/F sections 2 a through 2 c is in a connecting state.

[0061] (Second Embodiment)

[0062] The following description deals with another embodiment of thepresent invention with reference to FIG. 4 and FIG. 5. Note that samereference numerals and symbols are assigned to structures having samefunctions as those of the foregoing first embodiment, and note thattheir descriptions are omitted here.

[0063] A data transmission apparatus in accordance with the presentembodiment has a similar arrangement to the data transmission apparatus1 shown in FIG. 1, except that a control section whose arrangement isdifferent from the foregoing control section 4. FIG. 4 is a blockdiagram showing a schematic arrangement of a control section 20 inaccordance with the present embodiment. The control section 20 differsfrom the control section 4 shown in FIG. 2 in that the operation of acontrol circuit 21 is different and that AND circuits 22 a, 22 b, and 22c are provided, and the other arrangement is similar to that shown inFIG. 2.

[0064] The control circuit 21 (power control section, output levelcontrol section) generates a power control signal 102 and output levelcontrol signals 110 a, 110 b, and 110 c in response to the connectingdetection signals 103 a through 103 c that have been supplied from thedetection sections 5 a through 5 c, respectively. The control circuit 21outputs the power control signal 102 thus generated to the power sourcesection 3, and outputs the output level control signals 110 a through 10c to the AND circuits 22 a through 22 c, respectively.

[0065] The AND circuits 22 a through 22 c are provided between themodulation/demodulation circuit 10 and the buffer circuits 12 a through12 c, respectively. The AND circuits 22 a through 22 c receive the datasignals 101 a through 101 c from the modulation/demodulation circuit 10,and receive the output level control signals 110 a through 110 c fromthe control circuit 21, respectively. The AND circuits 22 a through 22 coutput the data signals 101 a through 101 c to the buffer circuits 12 athrough 12 c, respectively, when the output level control signals 110 athrough 110 c have a logical level of “1”. Whereas, the AND circuits 22a through 22 c output signals, each having a logical level of “0”, tothe buffer circuits 12 a through 12 c, respectively, when the outputlevel control signals 110 a through 110 c have a logical level of “0”.

[0066]FIG. 5. is a truth table for the control unit 21, the truth tableshowing logical levels of the connecting detection signals 103 a through103 c and a logical level of a corresponding power control signal 102,and logical levels of output level control signals 110 a through 110 c.The operation in accordance with the truth table is realized by alogical circuit represented by a logical formulae: L(102)=L(103 a)+L(103b)+L(103 c); L(110 a)=L(103 a); L(110 b)=L(103 b); and L(110 c)=L(103c).

[0067] More specifically, the power control signal 102 generated by thecontrol circuit 21 of the present embodiment has the same logical levelas that of the control circuit 11 shown in FIG. 2 or FIG. 3. The outputlevel control signals 110 a through 110 c generated by the controlcircuit 21 have the same logical levels as those of the connectingdetection signals 103 a through 103 c, respectively.

[0068] In a data transmission apparatus 1 having the above arrangement,the control circuit generates the same power control signal 102 as thatgenerated by the data transmission apparatus 1 shown in FIG. 1 throughFIG. 3. This results in that the present data transmission apparatus 1has the same functions and effects as those of the data transmissionapparatus 1 shown in FIG. 1, FIG. 2, or FIG. 3. The present datatransmission apparatus 1 has the following additional functions andeffects.

[0069] In the present data transmission apparatus 1, connectingdetection signals, supplied from I/F sections that are in a connectingstate, have a logical level of “1”. Accordingly, the logical levels ofthe output level control signals become “1”, as is clear from FIG. 5.This allows the AND circuits to output the data signals that have beensupplied to the AND circuits to which the output level control signalsare supplied.

[0070] For example, when the I/F section 2 a is in a connecting state,the control circuit 21 outputs an output level control signal 110 awhose logical level is “1”. This is because the detection section 5 aoutputs a connecting detection signal 103 a whose logical level is “1”.Accordingly, the data signal 101 a which has been supplied to the ANDcircuit 22 a is outputted to the I/F section 2 a via the buffer circuit12 a for output-use.

[0071] In contrast, when at least one I/F section exists which is not ina connecting state, a connecting detection signal, supplied from adetection section that is connected to the I/F section, has a logicallevel of “0”. Accordingly, the logical levels of the output levelcontrol signals corresponding to the connecting detection signals become“0”, as is clear from FIG. 5. This allows the AND circuit, to which theoutput level control signal is supplied, to output a signal whoselogical level is “0”.

[0072] For example, when the I/F section 2 c is not in a connectingstate, the control circuit 21 outputs an output level control signal 110c whose logical level is “0”. This is because the detection section 5 coutputs a connecting detection signal 103 c whose logical level is “0”.Accordingly, the signal, which has been supplied to the I/F section 2 cfrom the AND circuit 22 c via the buffer circuit 12 c for output-use,has a logical level of “0”.

[0073] Thus, the I/F section 2 a which is in a connecting state convertsthe data signal 101 a supplied from the modulation/demodulation circuit10 into the optical signal, and transmits the optical signal to anexternal device via the plug 6 a and the optical fiber 7 a, whereas theI/F section 2 c which is not a connecting state receives a signal whoselogical level is “0”. The light emitting element of the I/F section 2 cwill never emit the light. The foregoing risk, caused by the lightemitted outward from the I/F section which is not in a connecting state,can be avoided for each I/F section. In an I/F section in which thepower consumption is greater during a light emitting state than duringstopping of the light emitting, it is possible to obtain the effect ofthe saving of the power consumption. Further, it is possible to preventthe deterioration of the light emitting element in an I/F section whichis not a connecting state. This is because the stopping of emitting ofthe light is kept in the light emitting element of such an I/F section.

[0074] Note that the foregoing description deals with the case where thestopping of emitting of the light in the light emitting element of theI/F section 2 c is realized by the arrangement in which (a) the ANDcircuits 22 a through 22 c are provided in the control section 20 and(b) the data signals whose logical level are “0” are supplied to the I/Fsections 2 a through 2 c from the control section 20. The arrangementmay be replaced by an arrangement in which (a) an enable signal issupplied to the I/F sections 2 a through 2 c from the control circuit 21of the control section 20 and (b) the stopping of emitting of the lightin the I/F sections 2 a through 2 c is carried out in response to theenable signal. In the case where the supplying of the electric power tothe I/F sections is stopped, it is preferable that transmitting linesfor the data signals and a transmitting line for the enable signal havehigh impedance, respectively. This ensures to avoid a failure of aninternal circuit in the control section or the I/F section.

[0075] (Third Embodiment)

[0076] The following description deals with a further embodiment inaccordance with the present invention with reference to FIG. 6 and FIG.7. Note that same reference numerals and symbols are assigned tostructures having same functions as those of the foregoing embodiments,and note that their descriptions are omitted here.

[0077] An input device in accordance with the present embodiment has asimilar arrangement to the data transmission apparatus 1 shown in FIG.1, except that a control section whose arrangement is different from thecontrol section 4 is provided. FIG. 6 is a block diagram showing aschematic arrangement of a control section 30. The control section 30 ofthe present embodiment has a similar arrangement to the control section20 shown in FIG. 4, except that a control circuit operates in adifferent manner and that buffer circuits 32 a, 32 b, and 32 c foroutput-use are three-state buffer circuits, respectively.

[0078] The control circuit 31 (power control section, output levelcontrol section, and output permission control section) generates apower control signal 102, output level control signals 110 a through 10c, and an output buffer control signal 120 in response to connectingdetection signals 103 a through 103 c from detection sections 5 athrough 5 c, respectively. The power control signal 102 is supplied to apower source section 3. The output level control signals 110 a through110 c are supplied to AND circuits 22 a through 22 c, respectively. Theoutput buffer control signal 120 is supplied to three-state buffercircuits 32 a through 32 c for output-use, respectively.

[0079] The three-state buffer circuits 32 a through 32 c for output-useoutput signals from the AND circuits 22 a through 22 c, respectivelywhen the output buffer control signal 120 has a logical level of “1”,whereas they are fixed to high impedance when the output buffer controlsignal 120 has a logical level of “0”.

[0080]FIG. 7. is a truth table for the control unit 31, the truth tableshowing logical levels of the connecting detection signals 103 a through103 c and a logical level of a corresponding power control signal 102,logical levels of output level control signals 110 a through 110 c, anda logical level of the output buffer control signal 120, respectively.The operation in accordance with the truth table is realized by alogical circuit represented by a logical formulae: L(102)=L(120)=L(103a)+L(103 b)+L(103 c); L(110 a)=L(103 a); L(110 b)=L(103 b); and L(110c)=L(103 c).

[0081] More specifically, the power control signal 102 generated by thecontrol circuit 31 of the present embodiment has the same logical levelas that of the control circuit 11 shown in FIG. 2 or FIG. 3. Like theoutput level control signals 110 a through 110 c generated by thecontrol circuit 21 shown in FIG. 4 or FIG. 5, the output level controlsignals 110 a through 110 c generated by the control circuit 31 have thesame logical levels as those of the connecting detection signals 103 athrough 103 c, respectively. The output buffer control signal 120generated by the control circuit 31 has the same logical level as thatof the power control signal 102.

[0082] In a data transmission apparatus 1 having the above arrangement,the control circuit generates the same power control signal 102 as thatgenerated by the data transmission apparatus 1 shown in FIG. 1, FIG. 2,or FIG. 3. This results in that the present data transmission apparatus1 has the same functions and effects as those of the data transmissionapparatus 1 shown in FIG. 1, FIG. 2, or FIG. 3. In a data transmissionapparatus 1 having the above arrangement, the control circuit alsogenerates the same output level control signals 110 a through 110 c asthose generated by the data transmission apparatus 1 shown in FIG. 4 orFIG. 5. This results in that the present data transmission apparatus 1has the same functions and effects as those of the data transmissionapparatus 1 shown in FIG. 4 or FIG. 5. The present data transmissionapparatus 1 has the following additional functions and effects.

[0083] In the present data transmission apparatus 1, when none of I/Fsections 2 a through 2 c is in a connecting state, the control circuit31 outputs a power control signal 102 having a logical level of “0” to apower source section 3. On this account, no electric power is suppliedto the I/F sections 2 a through 2 c. Further, when the output buffercontrol signal 120 having a logical level of “0” is supplied to therespective three-state buffer circuits 32 a through 32 c for output-use,the three-state buffer circuits 32 a through 32 c for output-use arefixed to high impedance, respectively. This allows the data signals 101a through 101 c not to be supplied to the I/F sections 2 a through 2 cfrom the buffer circuits 32 a through 32 c.

[0084] By the way, the following problem arises, depending on what kindof signal format is used between the control section 30 and the I/Fsections 2 a through 2 c. Namely, an internal circuit of the controlsection 30 or the I/F sections 2 a through 2 c is likely to go belly upwhen signals are inputted or outputted to the I/F sections 2 a through 2c while no electric power is supplied to the I/F sections 2 a through 2c. For example, it is assumed that the control section 30 and the I/Fsections 2 a through 2 c are connected in accordance with a differentialsignal format. When signals are supplied to the I/F sections 2 a through2 c to which no electric power is supplied, relatively a great currentis flown into each power source circuit in the I/F sections 2 a through2 c via each input protection diode of the I/F sections 2 a through 2 c.As a result, it is likely that driving transistors for driving the datasignals 101 a through 101 c in the input protection diodes or thecontrol section 30 go belly up.

[0085] In contrast, according to the data transmission apparatus of thepresent embodiment, it is possible to avoid that the I/F sections 2 athrough 2 c, to which no electric power is supplied, receive anysignals, respectively. Accordingly, it is possible to avoid that theabove-described problem occurs.

[0086] Since the I/F section 2 c that is not in a connecting state doesnot receive any data from the control section 30, the I/F section 2 cwill never transmit any data to an external device. Thus, it is possibleto realize the power saving of the I/F section 2 c.

[0087] (Fourth Embodiment)

[0088] The following description deals with a further embodiment inaccordance with the present invention with reference to FIG. 8 throughFIG. 10. Note that same reference numerals and symbols are assigned tostructures having same functions as those of the foregoing embodiments,and note that their descriptions are omitted here.

[0089] A data transmission apparatus 40 shown in FIG. 8 has a similararrangement to that of the data transmission apparatus 1 shown in FIG.1, except that (i) three power source sections 3 a, 3 b, and 3 c areprovided in place of a single power source section 3, and (ii) a controlsection 41, having a different arrangement than the control section 4,is provided.

[0090] The power source sections 3 a through 3 c supply the electricpower to the I/F sections 2 a through 2 c in response to power controlsignals 102 a, 102 b, and 102 c from the control section 41,respectively, via power supply lines 103 a, 103 b, and 103 c.

[0091] In the present embodiment, like the foregoing embodiments, thepower control signals 102 a through 102 c are digital signals, and thepower source sections 3 a through 3 c (a) supply the electric power tothe I/F sections 2 a through 2 c, respectively, when the power controlsignals 102 a through 102 c have a logical level of “1”, whereas (b) noelectric power is supplied to the I/F sections 2 a through 2 c when thepower control signals 102 a through 102 c have a logical level of “0”.

[0092]FIG. 9 is a block diagram showing a schematic arrangement of thecontrol section 41. The control section 41 of the present embodiment hasa similar arrangement to the control section 30 shown in FIG. 6, exceptthat a control circuit 42 has a different circuitry than the controlcircuit 31.

[0093] The control circuit 42 (power control section, output levelcontrol section, output permission control section, individual powercontrol section, output control section, and switching section)generates power control signals 102 a through 102 c, output levelcontrol signals 110 a through 110 c, and output buffer control signals120 a through 120 c in response to connecting detection signals 103 athrough 103 c from detection sections 5 a through 5 c, respectively. Thepower control signals 102 a through 102 c are supplied to power sourcesections 3 a through 3 c, respectively. The output level control signals110 a through 110 c are supplied to AND circuits 22 a through 22 c,respectively. The output buffer control signals 120 a through 120 c aresupplied to three-state buffer circuits 32 a through 32 c foroutput-use, respectively.

[0094] A mode signal 130 is externally supplied to the control circuit42 in the control section 41. In response to the mode signal 130, theoperations of the present embodiment and similar operations to those ofthe data transmission apparatus 1 shown in FIG. 6 or FIG. 7 areswitched.

[0095]FIG. 10. is a truth table for the control unit 42, the truth tableshowing logical levels of the connecting detection signals 103 a through103 c, a logical level of the mode signal 130, corresponding powercontrol signals 102 a through 102 c, logical levels of output levelcontrol signals 110 a through 110 c, and logical levels of the outputbuffer control signals 120 a through 120 c, respectively. The operationin accordance with the truth table is realized by a logical circuitrepresented by a logical formulae: L(102 a)=L(120 a)=not L(130)*(L(103a)+L(103 b)+L(103 c))+L(130)*L(103 a); L(102 b)=L(120 b)=notL(130)*(L(103 a)+L(103 b)+L(103 c))+L(130)* L(103 b); L(102 c)=L(120c)=not L(130)*(L(103 a)+L(103 b)+L(103 c))+L(130)*L(103 c); L(110a)=L(103 a); L(110 b)=L(103 b); and L(110 c)=L(103 c). Note in thelogical formulae that “not” indicates a logical inversion and that “*”indicates a logical product.

[0096] In the data transmission apparatus 40 having the abovearrangement, when the mode signal 130 has a logical level of “0”, it ispossible to obtain similar functions and effects to those of the datatransmission apparatus 1 shown in FIG. 6 or FIG. 7, whereas, when themode signal 130 has a logical level of “1”, it is possible to carry outthe power control for each of the I/F sections 2 a through 2 c.

[0097] Thus, although the number of the components increases due to theincreasing of the number of the power source sections 3 a through 3 caccording to the data transmission apparatus 40 of the presentinvention, the power control is delicately carried out with respect toeach of the I/F sections 2 a through 2 c. It is possible to further savethe power consumption, accordingly.

[0098] Further, in the data transmission apparatus 40 of the presentembodiment, a mode signal having a logical level of “0” is supplied whena single power source section 3 carries out the power control for all ofthe I/F sections 2 a through 2 c, whereas, a mode signal having alogical level of “1” is supplied when the power source sections 3 athrough 3 c carry out the power controls for the I/F sections 2 athrough 2 c, respectively. This ensures to carry out the power controlin accordance with the number of the power source sections, therebyenabling to save the power consumption. Thus, the control section 41 ofthe present embodiment can carry out the power control in accordancewith the number of the power source sections. This means that it ispossible to hope the volume efficiency when the control section 41 isprovided in an integration manner.

[0099] The above description of the embodiments deals with a case wherethe I/F sections, corresponding to the two-way communication, areprovided. However, the present invention is not limited to such a case,i.e., the present invention may be applied to a case where the I/Fsections are transmitters which carry out outputting only or may beapplied to a case where the I/F sections are receivers which carry outinputting only.

[0100] In the above description, the control section is shown as anindependent component. However, the present invention is not limited tothis, i.e., the present invention may be realized by alternativecomponent, having other functions, such as software executed by amicroprocessor contained in the data transmission apparatus.

[0101] It is also possible to incorporate one part of the functions ofthe control section into the I/F section(s). For example, the followingarrangement may be possible: the buffer circuits 12 a through 12 c, thebuffer circuits 13 a through 13 c, and the AND circuits 22 a through 22c, each shown in FIG. 4, are provided in the I/F sections 2 a through 2c, respectively; and the data signals 101 a through 101 c outputted fromthe modulation/demodulation circuit 10 and the output level controlsignals 110 a through 110 c are supplied to the I/F sections 2 a through2 c, respectively.

[0102] The description has dealt with a case in which a positive logicis adopted. However, the present invention is not limited to this, i.e.,the present invention may be applied to a circuit which operates inaccordance with a negative logic. For example, the present invention maybe applied to a data transmission apparatus in which the turning off iscarried out when a level of “1”, is supplied to an I/F section, whereasthe turning on is carried out when a level of “0” is supplied to the I/Fsection.

[0103] The description has dealt with (a) a case where the embodiment inwhich the AND circuits 22 a through 22 c are added to the embodiment(corresponding to FIG. 4 and FIG. 5) in which the power control signal102 is supplied to the power source section 3 so as to carry out thepower control, and (b) a case where the embodiment in which thethree-state buffer circuits 32 a through 32 c for output-use are addedto the embodiment (corresponding to FIG. 6 and FIG. 7), respectively.Note that the provision of AND circuits or three-state buffer circuitsensures to realize the effect of saving of the power consumption in theI/F section(s), without carrying out the foregoing power control.

EXAMPLE

[0104] The following description deals with a case where the datatransmission apparatus of the above described embodiment is applied tothe IEEE Std 1394 serial bus standard.

[0105]FIG. 11 is a block diagram showing a schematic arrangement of adata transmission apparatus 50 which is obtained by applying the datatransmission apparatus 1 shown in FIG. 1 to the IEEE Std 1394 serial busstandard. Note that this is mere one example. The IEEE Std 1394 serialbus standard is a communication standard which is used in householdelectronic appliances such as audiovisual instruments. According to thestandard, the link-up is carried out via a tree structure topology,thereby giving rise to the tendency that a single instrument includes aplurality of I/F sections. No instrument main body is adopted because ofthe realization of the trunk function. This causes the parts involved inthe communication of the serial bus to be likely to operate even whileno electric power is supplied.

[0106] Because of being used in the household electronic appliances, theIEEE Std 1394 serial bus standard having the above property is requiredto save the power consumption and to reduce the production cost. In anOP i. LINK specification that is a standard obtained by extending theIEEE Std 1394 serial bus standard and in an IEEE Std 1394b serial busstandard, a specification for communication with optical fibers 7 a and7 b is set up. In these standards, it is required to avoid, during aperiod in which no communication is carried out, that opticaltransceivers 51 a, 51 b, and 51 c output the coherent light or outputthe high-intensity light so as to damage the human eyes and/or so as toshorten the lifetime of light emitting devices.

[0107] The data transmission apparatus and the control method thereof inaccordance with the present invention are in conformity with the aboverequirements.

[0108] In the IEEE Std 1394 serial bus standard, a functioncorresponding to the control section is referred to as PHY or physicallayer. An LSI for realizing the function is referred to as PHY LSI.

[0109] According to the IEEE Std 1394 serial bus standard, an interfacebetween a PHY LSI 52 and its higher communication layer is referred toas PHY-LINK interface. A PHY LSI 52 may be replaced with other LSI whichis in conformity with the rule of the PHY-LINK interface.

[0110] In the data transmission apparatus of the present example, thefunction on the PHY side of the PHY-LINK interface can be realized by amodulation/demodulation circuit in the PHY LSI 52. The characterizingpart of the present invention is realized by a control circuit in thePHY LSI, AND circuits, and three-state buffer circuits for output-use.The constituent components of the present invention do not affect thePHY-LINK interface, accordingly. Therefore, it is possible to apply thedata transmission apparatus of the present example to an instrumentwhich is compliant with the existing IEEE Std 1394 serial bus standard.

[0111] When each of the control sections in the foregoing embodimentsand the above example is constituted by a microcomputer, the way how thecontrol section controls may be realized by a control program. Thecontrol program may be stored in a computer-readable recording medium.According to the present invention, the computer-readable recordingmedium may be (a) a memory such as a ROM (Read Only Memory) which isbuilt in or is connected with a universal computer so as to be processedby the universal computer or (b) a recording medium from which a programcan be read out by loading the recording medium into a program readdevice that is provided as an external storage device.

[0112] In each case, it may be arranged such that the stored program isexecuted by the access of the microprocessor, or it may be arranged suchthat a program is executed by reading out the stored program anddownloading to a program memory area of a RAM (Random Access Memory) orother memory. Here, it is assumed that the program for the downloadingis stored in advance in the apparatus main body.

[0113] The program medium is a recording medium which is detachablyprovided with respect to the main body, and may be a medium, whichfixedly carries the program, such as (a) a tape medium such as amagnetic tape or a cassette tape, (b) a disk medium such as (i) amagnetic disk such as a flexible disk or a hard disk or (ii) an opticaldisk such as CD-ROM/MO/MD/DVD, (c) a card medium such as an IC card(including a memory card) or an optical card, or (d) a semiconductormemory such as a mask ROM, EPROM, EEPROM, or a flash ROM.

[0114] The present invention has a system arrangement which can beconnected with communication networks including Internet. Like thedownloading of a program from a communication network, the presentinvention may adopt a medium which carries a program. In the case ofdownloading the program from the communication network, a program fordownloading the program may be stored in the apparatus main body or maybe installed via another recording medium.

[0115] Note that the content of the recording medium is not limited to aprogram, i.e., the content may be data.

[0116] As described above, a control method of a data transmissionapparatus, in accordance with the present invention, which includes (a)a plurality of I/F sections; (b) a power source section; and (c)detection sections, includes the step of controlling the electric powersuch that the electric power is supplied to all of the I/F sections fromthe power source section when the detection sections detect that atleast one I/F section is in a connecting state, and such that noelectric power is supplied to the I/F sections from the power sourcesection when the detection sections detect that none of the I/F sectionsis in a connecting state.

[0117] With the arrangement, no electric power is supplied to the I/Fsections from the power source section when the detection sectionsdetect that none of the I/F sections is in a connecting state. Thisensures to save the power consumption, which is an effect derived fromthe above control method. Further, the provision of a single powersource section ensures another effect that the number of the componentsis reduced compared with the case where the power source sections whosenumber is equal to that of the I/F sections are provided for the purposeof saving the power consumption.

[0118] In the control method of the present invention, it is preferablethat (i) when the detection sections detect that an I/F section is in aconnecting state when transmitting a data to the external device via theI/F section, the data is controlled so as to be outputted to the I/F,and (ii) when the detection sections detect that the I/F section is notin a connecting state, a signal is controlled so as to be outputted tothe I/F section, the signal causing the I/F section to transmit to theexternal device a signal whose output level is a low level.

[0119] With the control method, it is controlled such that when the I/Fsection is in a connecting state when transmitting a data the externaldevice via the I/F section, the data is outputted to the I/F section.This allows the I/F section, which is in a connecting state, to transmitthe data to the external device. In contrast, it is controlled such thatwhen the I/F section is not in a connecting state when transmitting thedata to the external device via the I/F section, a signal is outputtedto the I/F section, the signal causing the I/F section to output to theexternal device a signal whose output level is a low level. This causesthe output level of the I/F section, which is not in a connecting state,to be lowered, thereby ensuring to realize the saving of the powerconsumption.

[0120] Accordingly, the following effect is obtained. Namely, it ispossible to save the power consumption with respect to the I/F sectionthat is not in a connecting state, even in a case where the saving ofthe power consumption can not be carried out based on the electric powercontrol due to the fact that at least one I/F section is in a connectingstate.

[0121] In the control method of the present invention, it is preferableto control such that the data to be transmitted to the external deviceis outputted to a target I/F section when the detection sections detectthat at least one I/F section is in a connecting state, and none of theI/F sections receives the data when the detection sections detect thatnone of the I/F sections is in a connecting state.

[0122] With the control method, it is controlled such that when at leastone I/F section is in a connecting state, (a) the electric power issupplied to all of the I/F sections and (b) the data to be transmittedto the external device is outputted to a target I/F section. This allowsthe I/F section which is in a connecting state to transmit the data tothe external device. In contrast, it is controlled such that when noneof the I/F sections is in a connecting state, (i) the electric power issupplied to none of the I/F sections and (ii) none of the I/F sectionsreceives the data. This ensures that the data is not supplied to the I/Fsections to which no electric power is supplied.

[0123] Accordingly, the following effect is obtained. Namely, it ispossible to prevent the breakdown in the internal circuit of the I/Fsection, the breakdown being likely to occur when the data is suppliedto the I/F section to which no electric power is supplied.

[0124] In the control method of the present invention, it is preferablethat when the data transmission apparatus includes a plurality of powersource sections for supplying the electric power to the respectiveinterface sections, the controlling of the electric power is changedinto an individual power controlling in which the electric power issupplied from the power source sections only to the interface sectionsthat have been detected to be in a connecting state by the detectionsections.

[0125] With the control method, when the data transmission apparatusincludes a single power source section that supplies the electric powerto all of the I/F sections, the foregoing electric power control iscarried out. In contrast, when the data transmission apparatus includesa plurality of power source sections that supply the electric power tothe respective I/F sections, the controlling of the electric power ischanged into an individual power controlling in which the electric poweris supplied only to the I/F sections that have been detected to be in aconnecting state by the detection sections. This ensures the followingeffect. Namely, it is possible to realize the saving of the powerconsumption by carrying out the electric power control in accordancewith the number of the power source sections.

[0126] In the control method of the present invention, it is preferablethat when the individual power controlling is carried out, a data to betransmitted to the external device is controlled so as to be outputtedto the I/F section that has been detected to be in a connecting state bythe detection sections, and the data is controlled so as not to beoutputted to the I/F section that has been detected not to be in aconnecting state by the detection sections.

[0127] With the control method, it is controlled such that when theindividual power controlling is carried out, (a) no electric power issupplied to the I/F sections which are not in a connecting state and (b)the data is not outputted to the I/F sections which are not in aconnecting state. Accordingly, the following effect is obtained. Namely,it is possible to prevent the breakdown in the internal circuit of theI/F section, the breakdown being likely to occur when the data issupplied to the I/F section to which no electric power is supplied.

[0128] As described above, another control method of a data transmissionapparatus in accordance with the present invention, the apparatusincluding: (a) a plurality of I/F sections, each converting a data intoa predetermined transmitting format and transmitting it to an externaldevice; and (b) detection sections each detecting whether or not each ofthe I/F sections is in a connecting state with respect to the externaldevice, comprises the step of controlling so as: (i) to output the datato an I/F section, when the detection sections detect that the I/Fsection is in a connecting state when transmitting the data to theexternal device via the I/F section, and (ii) to output a signal to theI/F, the signal causing the I/F section to transmit to the externaldevice a signal whose output level is a low level, or not to output thedata to the I/F section, when the detection sections detect that the I/Fsection is not in a connecting state.

[0129] With the control method, the following effect is obtained.Namely, it is possible to save the power consumption by causing the I/Fsection which is not in a connecting state to have a low level or zero,even in a data transmission apparatus which does not carry out thesaving of the power consumption based on the electric power control ofthe I/F section.

[0130] As described above, a data transmission apparatus of a controlunit, in accordance with the present invention, the data transmissionapparatus including: (a) a plurality of I/F sections; (b) a single powersource section; (c) a control unit that controls the power sourcesection; and (d) detection sections each detecting whether or not eachof the I/F sections is in a connecting state with respect to theexternal device, and outputting a connecting detection signal to thecontrol unit. The control unit includes a power control section thatoutputs to the power source section a power control signal forcontrolling the electric power such that the electric power is suppliedto all of the I/F sections from the power source section when thedetection sections detect that at least one I/F section is in aconnecting state, and such that no electric power is supplied to the I/Fsections when the detection sections detect that none of the I/Fsections is in a connecting state.

[0131] With the arrangement, although only a single power source sectionis provided, the electric power is supplied from the power sourcesection to none of the I/F sections in accordance with the controllingof the control unit when none of the I/F sections is in a connectingstate, thereby obtaining the following effect. Namely, it is possible torealize the saving of the power consumption with few components.

[0132] As described above, in a control unit of a data transmissionapparatus in accordance with the present invention having the abovearrangement, it is preferable to further include an output level controlsection that carries out controlling in accordance with the connectingdetection signals outputted from the detection sections such that: whenthe detection sections detect that the I/F section is in a connectingstate when transmitting a data to the external device via the I/Fsection, the data is outputted to the I/F section, and when thedetection sections detect that the I/F section is not in a connectingstate, a signal is outputted to the I/F section, the signal causing theI/F section to transmit to the external device a signal whose outputlevel is a low level.

[0133] With the arrangement, the control unit controls the outputting ofthe data to the I/F section in accordance with the connecting detectionsignal. More specifically, when the I/F section is in a connecting statewhen transmitting a data to the external device via the I/F section, thedata is outputted to the I/F section, whereas when the I/F section isnot in a connecting state, a signal is outputted to the I/F section, thesignal causing the I/F section to output to the external device a signalwhose output level is a low level.

[0134] At this time, in the data transmission apparatus, when the I/Fsection is in a connecting state when transmitting a data to theexternal device via the I/F section, the data is outputted to the I/Fsection in accordance with the controlling of the control unit. Thisallows the I/F section, which is in a connecting state, to transmit thedata to the external device. And, in the data transmission apparatus,when the I/F section is not in a connecting state when transmitting adata to the external device via the I/F section, a signal is outputtedto the I/F section, the signal causing the I/F section to output to theexternal device a signal whose output level is a low level. This allowsthe output level of the I/F section, which is not in a connecting state,to be lowered, thereby ensuring to realize the saving of the powerconsumption.

[0135] Thus, even in a case where it is not possible to carry out thesaving of the power consumption based on the electric power controllingbecause any of the I/F sections is in a connecting state, the followingeffect is obtained. Namely, it is possible to realize the saving of thepower consumption with respect to the I/F section which is not in aconnecting state.

[0136] As described above, in the control unit of the present invention,it is preferable to further include an output permission control sectionthat carries out controlling in accordance with the connecting detectionsignals outputted from the detection sections such that: the data to betransmitted to the external device is outputted to a target I/F sectionwhen the detection sections detect that at least one I/F section is in aconnecting state, and such that none of the I/F sections receives thedata when the detection sections detect that none of the I/F sections isin a connecting state.

[0137] With the arrangement, the control unit controls the outputting ofthe data to the I/F section in accordance with the connecting detectionsignal. More specifically, when the I/F section is in a connecting statewhen transmitting a data to the external device via the I/F section, thedata is outputted to the I/F section, whereas when the I/F section isnot in a connecting state, the data is not outputted to the I/F section.

[0138] At this time, in the data transmission apparatus, when any of theI/F sections is in a connecting state, it is controlled such that (a)the electric power is supplied to all of the I/F sections and (b) thedata is outputted to a target I/F section, in accordance with thecontrolling of the control unit, respectively. This allows the I/Fsection, which is in a connecting state, to transmit the data to theexternal device. In contrast, it is controlled such that when none ofthe I/F sections is in a connecting state, (1) the electric power issupplied to none of the I/F sections and (2) the data is supplied tonone of the I/F sections. This ensures that the data is not supplied tothe I/F sections to which the electric power is not supplied.

[0139] Accordingly, the following effect is obtained. Namely, it ispossible to prevent the breakdown in the internal circuit of the I/Fsection, the breakdown being likely to occur when the data is suppliedto the I/F section to which no electric power is supplied.

[0140] As described above, in the control unit of the present invention,when said data transmission apparatus includes a plurality of powersource sections for supplying the electric power to the respectiveinterface sections, it is preferable to further include: (a) anindividual power control section that controls the power source sectionsin accordance with the connecting detection signals such that theelectric power is supplied only to the interface sections that have beendetected to be in a connecting state by the detection sections; and (b)a switching section that switches from said power control section tosaid individual power control section.

[0141] With the control unit, when the data transmission apparatusincludes a single power source section that supplies the electric powerto all of the I/F sections, the foregoing electric power control iscarried out by the foregoing individual power control section. Incontrast, when the data transmission apparatus includes a plurality ofpower source sections that supply the electric power to the respectiveI/F sections, the controlling of the electric power is changed by theswitching section into an individual power controlling of the individualpower control section from the power controlling of the power controlsection. This ensures to output to each of the power source section apower control signal for controlling the power source section so as tosupply the electric power only to the I/F section which has beendetected to be in a connecting state by the detection section.

[0142] At this time, in the data transmission apparatus, (a) when thesingle power source section carries out the power controlling of all ofthe I/F sections, the power controlling is carried out by the powercontrol section of the control unit and (B) when the power sourcesections carry out the power controlling of the respective I/F sections,the power controlling is carried out by the individual power controlsection of the control unit.

[0143] Accordingly, the following effect is obtained. Namely, it ispossible to realize the saving of the power consumption by carrying outthe power controlling in accordance with the number of the power sourcesections. The control unit can carry out the power control in accordancewith the various number of the power source sections. This ensures theversatility and the following effect. Namely, it is possible to hope themass production.

[0144] As described above, in the control unit of the present invention,it is preferable to further include an output control section thatcontrols in accordance with the connecting detection signals outputtedfrom the detection sections such that: a data to be transmitted to theexternal device is outputted to the I/F section that has been detectedto be in a connecting state by the detection sections, and the data isnot outputted to the I/F section that has been detected not to be aconnecting state by the detection sections.

[0145] With the arrangement, it is controlled such that when theindividual power controlling is carried out, (a) no electric power issupplied by controlling of the individual power control section to theI/F sections which are not in a connecting state and (b) the data is notoutputted by controlling of the output control section to the I/Fsections which are not in a connecting state. Accordingly, the followingeffect is obtained. Namely, it is possible to prevent the breakdown inthe internal circuit of the I/F section, the breakdown being likely tooccur when the data is supplied to the I/F section to which no electricpower is supplied.

[0146] A data transmission apparatus having a control unit in accordancewith the present invention includes: (a) a plurality of I/F sections;(b) a control unit that controls outputting of the data to the I/Fsections; and (c) detection sections. The control unit includes: anoutput control section that controls the outputting of the data inaccordance with the connecting detection signal such that: when thedetection sections detect that the interface section is in a connectingstate when transmitting a data to the external device via the I/Fsection, the data is outputted to the I/F section, and when thedetection sections detect that the I/F section is not in a connectingstate, (a) a signal is outputted to the I/F section, the signal causingthe I/F section to transmit to the external device a signal whose outputlevel is a low level, or (b) the data is not outputted to the I/Fsection.

[0147] With the arrangement, even in a data transmission apparatus whichdoes not carry out the saving of the power consumption based on thepower control of the I/F section, it is possible to realize the savingof the power consumption. This is because the output level of the I/Fsection which is not in a connecting state becomes a low level or zeroin accordance with the controlling of the output control section.

[0148] Each of the control units may carry out data communications whichare in conformity with IEEE Std 1394 serial bus standard.

[0149] As described earlier, a data transmission apparatus in accordancewith the present invention, includes: (a) a plurality of I/F sections;(b) at least one power source section; (c) any one of the control unitsthat have been described; and (d) detection sections.

[0150] With the arrangement, it is possible to obtain the same effect asthe foregoing effect.

[0151] It is possible for a computer to carry out the control method ofthe data transmission apparatus, when a control program corresponding tothe control method of the data transmission apparatus is executed by thecomputer. When the control program of the data transmission apparatus isrecorded in a computer-readable recording medium, it is possible for anycomputer to carry out the control method of the data transmissionapparatus.

[0152] The specific embodiment and example described in “BEST MODE FORCARRYING OUT THE INVENTION” are only to clarify technical contents ofthe present invention. The present invention is therefore not to beinterpreted in a narrow sense as being limited by such specificexamples. In other words, the present invention may be varied in manyways within the scope of the spirit of the present invention and withinthe scope of the following claims.

INDUSTRIAL APPLICABILITY

[0153] The present invention provides a control method of a datatransmission apparatus, a control unit of the data transmissionapparatus, the data transmission apparatus, a control program of thedata transmission apparatus, and a recording medium in which the controlprogram is recorded each capable of saving the power consumption of I/Fsections in the data transmission apparatus. This ensures to realize thesaving of the power consumption in the data transmission apparatus.

1. A control method of a data transmission apparatus, said apparatuscomprising: a plurality of interface sections, each converting a datainto a predetermined transmitting format and transmitting it to anexternal device; a power source section that supplies electric power tothe respective interface sections; and detection sections, eachdetecting whether or not each of the interface sections is in aconnecting state with respect to the external device, said controlmethod comprising the step of: controlling the electric power such thatthe electric power is supplied to all of the interface sections from thepower source section when the detection sections detect that at leastone interface section is in a connecting state, and such that noelectric power is supplied to the interface sections from the powersource section when the detection sections detect that none of theinterface sections is in a connecting state.
 2. The control method asset forth in claim 1, wherein: when the detection sections detect thatan interface section is in a connecting state when transmitting a datato the external device via the interface section, the data is controlledso as to be outputted to the interface section, and when the detectionsections detect that the interface section is not in a connecting state,a signal is controlled so as to be outputted to the interface section,the signal causing the interface section to transmit to the externaldevice a signal whose output level is a low level.
 3. The control methodas set forth in claim 1 or 2, wherein: the data to be transmitted to theexternal device is controlled so as not to be outputted to the interfacesection to which the electric power is not supplied in accordance withthe controlling of the electric power.
 4. The control method as setforth in claim 1, wherein: when said data transmission apparatusincludes a plurality of power source sections for supplying the electricpower to the respective interface sections, the controlling of theelectric power is changed into an individual power controlling in whichthe electric power is supplied from the power source sections only tothe interface sections that have been detected to be in a connectingstate by said detection sections.
 5. The control method as set forth inclaim 4, wherein: the data to be transmitted to the external device iscontrolled so as not to be outputted to the interface section to whichthe electric power is not supplied in accordance with the individualpower controlling.
 6. A control method of a data transmission apparatus,said apparatus comprising: a plurality of interface sections, eachconverting a data into a predetermined transmitting format andtransmitting it to an external device; and detection sections eachdetecting whether or not each of the interface sections is in aconnecting state with respect to the external device, said controlmethod comprising the step of controlling so as: to output the data toan interface section, when the detection sections detect that theinterface section is in a connecting state when transmitting the data tothe external device via the interface section, and (a) to output asignal to the interface section, the signal causing the interfacesection to transmit to the external device a signal whose output levelis a low level, or (b) not to output the data to the interface section,when the detection sections detect that the interface section is not ina connecting state.
 7. A control unit of a data transmission apparatus,said data transmission apparatus, comprising: a plurality of interfacesections, each converting a data into a predetermined transmittingformat and transmitting it to an external device; a power source sectionthat supplies electric power to the respective interface sections; acontrol unit that controls the power source section; and detectionsections each detecting whether or not each of the interface sections isin a connecting state with respect to the external device, andoutputting a connecting detection signal to the control unit; and saidcontrol unit, comprising: a power control section that outputs to saidpower source section a power control signal for controlling the electricpower (i) such that the electric power is supplied to all of theinterface sections from the power source section when the detectionsections detect that at least one interface section is in a connectingstate, and (ii) such that no electric power is supplied to the interfacesections when the detection sections detect that none of the interfacesections is in a connecting state.
 8. The control unit as set forth inclaim 7, further comprising an output level control section that carriesout controlling in accordance with the connecting detection signalsoutputted from said detection sections such that: when the detectionsections detect that the interface section is in a connecting state whentransmitting a data to the external device via the interface section,the data is outputted to the interface section, and when the detectionsections detect that the interface section is not in a connecting state,a signal is outputted to the interface section, the signal causing theinterface section to transmit to the external device a signal whoseoutput level is a low level.
 9. The control unit as set forth in claim 7or 8, further comprising: an output permission control section thatcontrols the data, which is to be transmitted to the external device, soas not to be outputted to the interface section to which the electricpower is not supplied in accordance with the controlling of the powercontrol section.
 10. The control unit as set forth in claim 7, furthercomprising, when said data transmission apparatus includes a pluralityof power source sections for supplying the electric power to therespective interface sections: an individual power control section thatcontrols said power source sections in accordance with the connectingdetection signals such that the electric power is supplied only to theinterface sections that have been detected to be in a connecting stateby said detection sections; and a switching section that switches fromsaid power control section to said individual power control section. 11.The control unit as set forth in claim 10, further comprising: an outputcontrol section that controls the data, which is to be transmitted tothe external device, so as not to be outputted to the interface sectionto which the electric power is not supplied in accordance with thecontrolling of the individual power control section.
 12. A control unitof a data transmission apparatus, said data transmission apparatus,comprising: a plurality of interface sections, each converting a datainto a predetermined transmitting format and transmitting it to anexternal device; a control unit that controls outputting of the data tothe interface sections; and detection sections, each detecting whetheror not each of the interface sections is in a connecting state withrespect to the external device, and outputting a connecting detectionsignal to the control unit; said control unit, comprising: an outputcontrol section that controls the outputting of the data in accordancewith the connecting detection signal such that: when the detectionsections detect that the interface section is in a connecting state whentransmitting a data to the external device via the interface section,the data is outputted to the interface section, and when the detectionsections detect that the interface section is not in a connecting state,(i) a signal is outputted to the interface section, the signal causingthe interface section to transmit to the external device a signal whoseoutput level is a low level, or (ii) the data is not outputted to theinterface section.
 13. The control unit as set forth in claim 7, 8, 9,10, 11, or 12, wherein said control unit carries out data communicationswhich are in conformity with IEEE Std 1394 serial bus standard.
 14. Adata transmission apparatus, comprising: a plurality of interfacesections, each converting a data into a predetermined transmittingformat and transmitting it to an external device; at least one powersource section that supplies electric power to the interface sections; acontrol unit recited in claim 7, 8, 9, 10, 11, 12, or 13; and detectionsections, each detecting whether or not each of the interface sectionsis in a connecting state with respect to the external device, andoutputting a connecting detection signal to the control unit.
 15. Acontrol program of a data transmission apparatus causing a computer tocarry out the control method recited in claim 1, 2, 3, 4, 5, or
 6. 16. Acomputer-readable recording medium in which the control program as setforth in claim 15 is recorded.